ROCK VARIATIONS. 51 
surrounded by it, is a mass of biotite schist between 30 and 40 feet 
long and 3 feet thick, striking north and dipping 35° east. In quar- 
rying, this mass has been cut from east to west. Under the micro- 
scope this is a coarse biotite quartz and feldspar (oligoclase) schist. 
It is probably of sedimentary origin. PL VII, Z?, shows part of the 
jagged edge of the lower portion of the inclusion and two isolated 
fragments of it in the granite. The granite below one of the pro- 
truding angles of the inclusion is badly stained by ferruginous water 
coining from the schist. In some parts of this inclusion there are 
streaks of pegmatite consisting of feldspar (oligoclase-andesine) and 
quartz. The period of its formation is uncertain. 
CONTACTS. 
At the Waldoboro quarry the original contact of the upper part of 
the granite mass with the lower part of the remnant of the schist 
mass, which once overlay that region and into which the granite was 
intruded, is exposed. (See PL IX, A, and p. 142.) This schist is a 
hornblende-biotite-quartz schist containing some andesine feldspar, 
ialso accessory titanite and zircon. It is a metamorphosed rock, prob- 
ably of sedimentary origin. At the opposite or southwest end of the 
quarry (see fig. 29) the relations between the schist and granite are 
very complex, and a considerable mass of pegmatite intervenes in 
places. The granite sends small dikes into the schist and also con- 
tains inclusions of it. The granite was erupted after or during the 
folding of the schist, otherwise it would have become a gneiss. 
MINERALS ON JOINT FACES. 
1 
Joint faces in granite are in some places coated with minerals which 
o not occur in the granite itself or but very sparsely. At the 
^;inds quarry, in Vinalhaven, one of the joint faces bears very 
jninute crystals of stilbite, a hydrous silicate of alumina, lime^ and 
oda,« also hematite. In other places the face is coated with a film 
)f crystalline calcite from one-tenth to one-fifth inch thick. Calcite 
Recurs also similarly at one of the Redbeach quarries. (See p. 166.) 
V thin coating of secondary fibrous muscovite or of epidote occurs 
t several quarries. At the W. B. Blaisdell quarry, in Franklin, 
ertain joints are coated with crystalline calcite to a thickness of 
ine-fourth inch, forming in places banded veins. (See p. 41.) A 
pin section of the granite away from the joint does not show any 
arbonate, but Mr. E. C. Sullivan, of the Survey (p. 94), found 0.24 
,|er cent of lime carbonate in a few ounces of the same specimen. 
|)ther joints in the same quarry with a different strike are coated 
ith pyrite, and from their rusty appearance are known by the 
01 
Determination by Mr. W. T. Schaller, of the United States Geological Survey. 
